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“神龙一号”加速器在束流调试初期出现了严重的BBU,该BBU是由偏心束流通过多功能腔时激励的TM_(110)模引起的.分别以解析分析、数值计算和实验测量等方法对多功能腔的高频特性进行分析.几种方法得到的TM_(110)模频率与实验结果吻合,而横向耦合阻抗则有倍数之差,但都证明多功能腔在TM_(110)模式下的横向耦合阻抗过大,是激励BBU的最主要的因素.为此,设计了对多功能腔其他功能不产生影响的可以轴向伸缩的网罩,用来屏蔽多功能腔间隙.使用网罩后效果非常显著,实验结果表明,BBU受到抑制,束流脉冲中的高频振荡消失.
A serious BBU occurred in the early stage of beam debugging of the “Shenlong One” accelerator, which was caused by the TM 110 mode stimulated by the eccentric beam passing through the multifunctional cavity. Analytical analysis, numerical calculation and experiment (110) mode frequency obtained by several methods is in good agreement with the experimental one, while the lateral coupling impedance has a multiple difference, but it is proved that the multi-function cavity has a good performance in TM 110 ) Mode is the most important factor that motivates the BBU.In order to do this, an axially retractable mesh mask that does not affect other functions of the multi-function chamber is designed to shield the multi-function gap. The effect is very significant after using the mesh cover. The experimental results show that the BBU is suppressed and the high frequency oscillation in the beam disappears.